Kérastase Resistance Strengthening Duo For Fine To Medium Hair is the ultimate haircare solution for weak and damaged hair. Including the Kérastase Resistance Bain Force Architecte Strengthening Shampoo and Fondant Extentioniste Length Strengthening Conditioner, this professional haircare duo cleanses, nourishes, and fortifies your hair from root to tip to repair, strengthen, and promote smooth, silky hair while preventing breakage and split ends.